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PHP - Superglobals

Superglobals in PHP are predefined variables that are accessible from any scope throughout a PHP script. They provide information about the server environment, request, and session management. Here are the main superglobals in PHP:

1. $_GET

$_GET is an associative array of variables passed to the current script via the URL parameters (query string) using the HTTP GET method.

Example: Assuming the URL is http://example.com/?name=John&age=30:

php
<?php
    echo $_GET['name']; // Outputs: John
    echo $_GET['age']; // Outputs: 30
    ?>

2. $_POST

$_POST is an associative array of variables passed to the current script via the HTTP POST method when using forms with method="post".

Example:

php
<form method="post" action="process.php">
        <input type="text" name="username">
        <input type="password" name="password">
        <button type="submit">Submit</button>
    </form>
    
    <?php
    echo $_POST['username']; // Accesses input from form submission
    ?>

3. $_REQUEST

$_REQUEST is a merged array containing $_GET, $_POST, and $_COOKIE variables. It can handle data from both GET and POST requests.

Example:

php
<?php
    echo $_REQUEST['name']; // Works for both GET and POST requests
    ?>

4. $_FILES

$_FILES is an associative array containing information about uploaded files via HTTP POST. It contains file upload information such as file name, file type, and file size.

Example:

php
<form method="post" action="upload.php" enctype="multipart/form-data">
        <input type="file" name="file">
        <button type="submit">Upload</button>
    </form>
    
    <?php
    $file = $_FILES['file'];
    echo $file['name']; // Outputs the uploaded file name
    ?>

5. $_COOKIE

$_COOKIE is an associative array of variables passed to the current script via HTTP cookies.

Example:

php
<?php
    echo $_COOKIE['username']; // Outputs the value of the 'username' cookie
    ?>

6. $_SESSION

$_SESSION is an associative array containing session variables available to the current script. It allows you to store user-specific data across multiple pages.

Example:

php
<?php
    // Start or resume session
    session_start();
    
    // Set session variables
    $_SESSION['username'] = 'John';
    
    // Access session variables
    echo $_SESSION['username']; // Outputs: John
    ?>

7. $_SERVER

$_SERVER is an array containing information such as headers, paths, and script locations. It provides server and execution environment information.

Example:

php
<?php
    echo $_SERVER['SERVER_NAME']; // Outputs the server's host name
    echo $_SERVER['REMOTE_ADDR']; // Outputs the IP address of the user
    ?>

8. $_ENV

$_ENV is an associative array containing environment variables available to the script. It's populated from the environment under which the PHP parser is running.

Example:

php
<?php
    echo $_ENV['PATH']; // Outputs the system's PATH environment variable
    ?>